In internal combustion engines, an oil pump is provided to circulate oil and maintain an acceptable level of oil pressure within the engine. It is well known to drive oil pumps using the rotational force generated by the crankshaft of the engine.
Most oil pumps that are driven by the crankshaft follow one of two well-known designs. The first places the pump directly on the crankshaft, such that the crankshaft passes through the rotor of the pump. Thus, the pump is arranged around the crankshaft itself. For example, in a pump that uses rotating vanes that move fluid between an inlet and an outlet, the crankshaft itself is the axis around which the vanes rotate.
The second well known arrangement is to locate the pump external to the internal combustion engine, such as by bolting the pump to an external portion of the internal combustion engine, or by otherwise supporting the oil pump with respect to the internal combustion engine. In such systems, the oil pump includes a pulley that is driven by a belt or a chain that is connected to a crankshaft pulley on the exterior of the internal combustion engine.
Both designs have their advantages and disadvantages. For example, locating the pump on the crankshaft simplifies assembly, but at the same time requires that the dimensions of the pump be increased, such that the crankshaft may pass through the pump. This results in an unnecessarily large size for the oil pump and places constraints on the design of the pump that tend to reduce its efficiency. Belt or chain driven oil pumps may be produced compactly, but require additional assembly steps in mounting the pump to the internal combustion engine.
It would be desirable to have an oil pump that simplifies assembly, operates efficiently, and is of relatively small size.